Causal Inference during Motion Perception and its Neural Basis

Host

Memming Park, Principal Investigator, Champalimaud Research

Venue

Seminar room

Abstract

If motion is always defined relative to a reference frame, what is the brain's reference frame for the perception of a moving object? A century of psychophysical studies has provided us with seemingly conflicting evidence about motion perception in a variety of reference frames: from egocentric, to world-centric, to reference frames defined by other moving objects. We present a hierarchical Bayesian model which describes how observed retinal velocities give rise to perceived velocities. The hierarchically recurring generative model motif represents each perceived object's motion in its natural reference frame which reflects the causal structure of the world. The degeneracy of object motion and reference frame motion is broken by a spike and slab prior reflecting the fact that most objects are exactly stationary in their natural reference frame. Data from three new psychophysical experiments quantitatively confirm key predictions of our model.
Finally, I will present a stepwise method for generating neural predictions from our, and other, Bayesian models of the brain, and for comparing them against each other using neural data. Interestingly, a neural circuit implementing a generalised version of divisive normalisation can generate the centre-surround tuning curves predicted by causal inference.

Biography

Ralf Haefner is a computational neuroscientist whose lab studies the neural and computational basis of perceptual inference. After getting a PhD in physics (Oxford) he was a postdoc with Bruce Cumming (NIH), Matthias Bethge (MPI Tübingen) and Jozsef Fiser (Brandeis), and is now an Associate Professor in Brain & Cognitive Science at the University of Rochester.
 

Register here.
 

About CR Colloquia Series

Champalimaud Research (CR) Colloquia Series is a seminar programme organised by the Champalimaud Centre for the Unknown to promote the discussion about the most interesting and significant questions in neuroscience and physiology & cancer with appointed speakers by the CR Community.